Author Topic: AAZ engine in a Passat 95, fuel cuts off at 2900 rpm (Read 5898 times)

doc_oc · « **on:** November 15, 2007, 09:26:51 am »

After the engine warmed up and was driven for at least 25-30 minutes, sometimes, rarely, the engine works fine up to 2900 than it bogs down, and the rpm drops. If I shift in next gear (rpm drop) it will work till 2900 again and will do the same thing.
Any idea why?
Just some other info about what's going on with the car, when I slow down, bellow 20, I hear a quick on/off relay sound (at least 4-5 clicks). Also, the car was not shutting off from the ignition when I bought it (I had to stall it) then all of a sudden it starting working (the car shuts off from the key).
I will change the fuel filter and run some diesel purge tonight...I donno what else to check for?
Thanks.

starrd · « **Reply #1 on:** November 15, 2007, 09:43:54 pm »

Maybe check the o-ring on the fuel shut-off on the injection pump. I have heard they can slide down and cause no shut off and low power.

Also, the clicking has to do with the boost control, which is triggered by a switch on top of the injection pump.

doc_oc · « **Reply #2 on:** November 16, 2007, 09:39:41 am »

Quote from: "starrd"

Maybe check the o-ring on the fuel shut-off on the injection pump. I have heard they can slide down and cause no shut off and low power.

Also, the clicking has to do with the boost control, which is triggered by a switch on top of the injection pump.

The clicking is the sound of a relay under the dashbord behind the ashtray.
I'll check the oring. Thanks.

starrd · « **Reply #3 on:** November 16, 2007, 09:51:38 am »

The relay (behind the ashtray) is triggered by the switch on top of the injection pump. Sorry, it is the EGR half-load switch which controls the EGR(not boost). That is not your problem. My car has this switch and relay, but no EGR valve - mine is always clicking.

doc_oc · « **Reply #4 on:** November 16, 2007, 10:50:10 am »

So is it normal to click so erratic? Or is there anything I could change/fix?
Thanks.

jtanguay · « **Reply #5 on:** November 16, 2007, 10:52:38 am »

does it click proportional to the position of the accel pedal? like if you floor it?

starrd · « **Reply #6 on:** November 16, 2007, 10:53:20 am »

Yes that is normal, you'll find if you hold the throttle in the spot where the switch switches, it is worse. I usually push past that point and then it is not as erratic.

commuter boy · « **Reply #7 on:** November 16, 2007, 09:20:46 pm »

My AAZ Passat also does the low speed relay clicking sound from behind the ashtray, but my switch on top of the pump is undone and not connected to the throttle mechanism anymore, so it's not that.

I assumed it had something to do with the AC and low idle speeds.

starrd · « **Reply #8 on:** November 18, 2007, 10:10:21 pm »

Did some research and found the following info regarding the relay "Click"

Exhaust gas is taken from the exhaust manifold 1 and returned to the intake pipe 3 via the
vacuum-controlled EGR valve 2.
Control switching is accomplished using vacuum from vacuum, pump 4 via the two-way valve 5 from
the EGR control module (J 287) 8. The EGR is switched (controlled) as follows:

- at temperatures under +50 C (engine cold), the EGR is shut off via the engine oil temperature sensor (preheat system) (G 27) 6.

- the EGR Part Throttle Switch (F 166) 7 on the injection pump insures that exhaust is only returned in the partial load range

- engine speed shut off is accomplished via the EGR control module (J 287) 8 and terminal W (9) of the generator. In this process, the EGR is interrupted for 2 seconds if engine speed exceeds 1200 rpm and is shut off at engine speeds greater than 3200 rpm

- The EGR is shut off by the altitude correction switch in the EGR control module 8 if altitude exceeds 1000 m

doc_oc · « **Reply #9 on:** November 19, 2007, 05:13:02 am »

Thanks for all the info.

I played a bit with the throtle and it does not seem to be throtle related.
If stopped and at idle, when you go past 1200 rpm you hear a click. If you let it idle again after 2 seconds it clicks again. So that makes it clear that the sound comes from the EGR relay.
The weird part is that every time I slow down (arround 25kph) with the engine at idle (coasting) that relay does not click only once...it does it at least 5 times (if not more) in 1-2 seconds.
Anyways...it's clear now.
How do you guys remove the EGR system? Is there a pipe to replace the EGR elbow on the intake manifold? What do you do with the relay/vacuum hose?

doc_oc · « **Reply #10 on:** November 26, 2007, 08:53:07 am »

I steel can't get this figures out. I changed the fuel filter and the same thing happens.

If I hit the go pedal hard...it goes till about 2900rpm than it just goes to idle.
I have a bunch of air bubbles in the fuel line and as soon as it goes to idle (it cuts the fuels almost) on the fuel return line from the pump to the filter it's all foam, that's how many bubbles are.
The car drives fine other than that.
Can a cracked fuel line that allow air in be the cause for this?

QuickTD · « **Reply #11 on:** November 26, 2007, 11:51:23 am »

Any air leak in the lines will cause this sort of problem. I've also seen bad cavitation and bubbles in the lines caused by a plugged check valve located near the sending unit/fuel pickup in the tank. The check valve is accessable trough the access panel in the trunk. I would carefully check all connections including the rubber bellows on the pickup inside the tank.

If it's only the return line that goes foamy at high speed then the problem could be with the pump drive shaft seal. This is easy to change on the older pumps but quite difficult on 95 and up AAZ pumps. The reason for the difficulty is that the later model pump sprocket hub is not keyed to the shaft, it must be positioned correctly at assembly. To perform this procedure as a do-it-yourselfer involves some very tricky special tools and very thorough knowledge of pump timing procedures. I would recommend the pump be taken to a shop for the repair. If the pump is not leaking externally from the shaft you could install a low pressure transfer pump, this relieves the vacuum on the seal and will temporarily solve your problem, though eventually the pump will start to leak from the shaft as the seal wears further.

doc_oc · « **Reply #12 on:** November 26, 2007, 12:00:40 pm »

Low pressure transfer pump like in a lift pump?
Between the tank and the fuel filter for example, to keep the pressure to the IP instead of the IP sucking all the way from the tank?
What pressure/volume do you recommend for the pump?
Coming from TDIs, I have a hard time understanding the timming procedure for the AAZs. Is there a DIY or any set of instructions for this?

QuickTD · « **Reply #13 on:** November 27, 2007, 07:34:15 am »

Quote from: "doc_oc"

Low pressure transfer pump like in a lift pump?
Between the tank and the fuel filter for example, to keep the pressure to the IP instead of the IP sucking all the way from the tank?
What pressure/volume do you recommend for the pump?

Thats right, a lift pump. A pump for a carburated gasser works good, 5-10psi. You don't want big pressure as it will alter the injection timing.

Quote

Coming from TDIs, I have a hard time understanding the timming procedure for the AAZs. Is there a DIY or any set of instructions for this?

The bentley manual is good, but doesn't cover the late model pump. I have a PDF document that outlines the new style sprocket procedure, PM with an Email address and I'll send it to you. No manual will give you the procedure to pull and retime the pump sprocket hub, that is normally done at the factory or at a bosch injection shop.